High pressure mercury vapor lamp provided with a cooling water jacket

ABSTRACT

A lamp assembly, which is a combination of a capillary type high-pressure mercury vapor lamp and a water cooling jacket, said combination being convenient for replacement and mounting of the lamp. The jacket also effectively absorbs the thermal radiation from the lamp and discharges air bubbles from the jacket.

[1 1 3,739,215 1 June 12, 1973 PRESSURE MERCURY VAPOR LAMP PROVIDED WITH A COOLING WATER l,897,587 2/1933 Pirani..........................

FOREIGN PATENTS OR APPLICATIONS 1,132,240

JACKET Inventor:

6/1962 Germany 313/47 Kaoru Murai, Tokyo, Japan d, A. Ponack n ell L 8. NE D Hh 0 CR mm .LWO f ya e O d R n 1 flm n Re i 8 mm MMEC E ty v yne ammV .m umd r8 PAA n W a 1 y k 0 T 1 m7 w mo S000 0H7 YAl I Q 6 e 1 .1. p who. AFA 1] 32 722 [.11

ABSTRACT [30] Foreign Application Priority Data A lamp assembly, which is a com bination of a capillary Dec. 24, 1970 Japan.................... 45/129811 type hi hr s re mercury vapor lamp and a water cooling jacket, said combination being convenient for [52] US. 313/24, 313/27, 313/42 replacement and mounting ofthe lamp Theyjacket also [51] Hill. H01] 61/52, H01] 61/35 effectively absorbs the thermal radiation from the lamp [58] Field Of Search.................... 313/24, 27 and discharges air bubbles from the jacket.

3 Claims, 2 Drawing Figures [56] References Cited UNITED STATES PATENTS 3,603,827 9/1971 Degawa et a1. 313/24 Patented June '12, 1973 2 Sheets-Sheet Kaoru murai,

INVENTOR B ZJMwC ATTORNEY s Patented June 12, 1973 2 Sheets-Sheet 2 Kaor u Mura i INVENTOR ATTORNEYs BACKGROUND OF THE INVENTION This invention relates to a high pressure mercury vapor lamp. More particularly, this invention relates to a combined structure of a capillary type high-pressure mercury vapor lamp and a water cooling jacket which is to be used during exciting the lamp.

In the conventional capillary type high-pressure mercury lamp, each of the electrodes is provided with a metallic base which is connected to a power supply.

In a water-cooling system for such a lamp, at least one of the electrodes must be insulated from the cooling water in order to establish an electrical insulation between the electrode and the water. For this reason, the metallic base of one electrode is covered with a rubber or plastic tube and joined at the opening of the jacket piping by means of, for example, a Wilson seal.

In the above arrangement, the insulating rubber or plastic tube provides only a poor conduction of heat and is not adequately heat-resistant, with the result that the inner surface of the rubber or plastic tube contacting the metallic base softens and expands in use and, over an extended period of time, is degraded and loses elasticity. This condition leads to water leaks, which break down the insulation between the electrodes. Usually, the water jacket is a double-tubing structure and a capillary type high-pressure mercury vapor lamp is mounted in the center of the inner tube, the lead from the ground electrode extending through the water in the outer piping and being connectedto the support structure. In the above arrangement, when replacing the mercury-vapor lamp, it is necessary to detach the entire jacket assembly from the body since the construction thereof generally is closed at one end and all the acess means are positioned at the other end, hold the assembly upright, remove the jacket tube and, finally, replace the lamp with a new one. In addition, when cooling water is admitted after lamp replacement, the air bubbles that are formed in the jacket tubing cannot be easily removed. Those disadvantages have heretofore prevented any water cooling system from wide acceptance in the field of mercury vapor lamps.

From another view, because the outer and inner tubes hithereto employed for the cooling of a capillary type high-pressure mercury vapor lamp are made of clear, colorless glass or plastic, they transmit the light having a broad spectral range from the ultraviolet to the infrared region. Therefore, when such a lamp is utilized in such processes as the production of printing plates, printed matrices and other printing operations involving the use of light, both the light in the ultraviolet region and the short wavelength region of visible light which is useful for exposure in the operations such as referred to above and the light in the long wavelength region of visible light and the infrared region (hereinafter called thermal radiation) which not is effective in said operations impinges upon the surface to be exposed and cause a temperature increase in the surface, so that both the film and sensitizing agent are adversely affected. Further, it has also been found that in such a light source adapted to be cooled by the water that air bubbles are removed from the lamp housing only with difficulty and they may cause uneven exposure or partial overheating of the materials or elements employed in the light source assembly thereby resulting, in some instances, in explosion of the lamp.

SUMMARY OF THE INVENTION It is an object of this invention to provide a watercooled high-pressure mercury vapor lamp free from the foregoing disadvantages.

Another object is to provide a capillary type highpressure mercury vapor lamp provided with a cooling water jacket which facilitates replacement of the lamp.

It is still another object of this invention to provide a high-pressure mercury vapor lamp which is adapted to effectively absorb thermal rays and in which air bubbles are easily and substantially completely removed from the jacket. 7

The above and other objects are accomplished by this invention which will hereinafter be described in detail.

The capillary type high-pressure mercury vapor lamp provided with a water jacket according to this invention is characterized in that while a conventional metallic base is used for one of the electrodes, a ceramic base is used for the other electrode. This ceramic base is formed in the shape of a hollow cylinder having a collar in the center of its axial length and is connected, at one end, to one end of a capillary type high-pressure mercury vapor lamp made of quartz by means of a heatresistant inorganic or organic cement. The lead from the discharge electrode extends through the interior of the ceramic tube and is connected to a metal strip .provided at the other end of said tube and, thence, to a power supply. Opposite ends of the lamp are directly connected to the power source, respectively by means of the openings provided at both ends of the water jacket tube.

.The central collar of the ceramic base prevents water leaks in such a manner that when the cooling water jacket tube is connected, rubber or plastic packings on both sides of the collar provide a water-tight seal. The inner tube of the double-tubing water jacket used in accordance with this invention is flared at its forward end so that gap between the outer and inner tubings at the flare is narrowed. The cooling water injected between the outer and inner tubes blows at a high velocity between the inner tube and the lamp, the velocity being increased at the gap narrowed by the flare, and flows out from the base of the inner tube. In this arrangement, when, for disassembly, the inflow of cooling water is suspended and the packing at the ceramic base joint at the tip of the jacket piping is loosened, the water within the jacket piping flows out through the outlet of the inner tube and, when the capillary type high-pressure mercury vapor lamp is detached, cooling water does not flow out. Therefore, replacement of the lamp can be effected with the jacket tube remaining attached to the body.

Furthermore, when cooling water is readmitted after lamp replacement, the air bubbles in the outer tube are forced out by the high-velocity water flow into the inner tube through its flared opening and, ultimately, removed. The removal of the air bubbles tending to dwell especially at the end part of the passage between the inner and outer tubings are effectively discharged due to the accelerated velocity which is caused by the narrow gap and the flared opening of the inner tubing.

In accordance 'with this invention, by fabricating either the outer tube or the inner tube, or both of them,

of a filter glass or plastic material which has a high transmittance to ultraviolet light and a high absorbance with respect to thermal radiation, it is possible to reduce'the amount of thermal radiation that acts upon the surface being irradiated and, accordingly, minimizes the temperature building on the surface.

Furthermore, because the inner and outer tubes having such a filter characteristic are in direct contact with cooling water, they are not appreciably heated even when they absorb the thermal radiation. Therefore, it is possible to prevent the destruction of the tubes, and at the same time, minimize the temperature increase of the illuminated surface due to thermal radiation.

The invention, and its objects and advantages, will become more apparent from the detailed description of the preferred embodiment presented below.

BRIEF DESCRIPTION OF THE DRAWINGS mercury vapor lamp provided with a cooling water jacket; and

FIG. 2 is a sectional view showing a high-pressure mercury vapor lamp having a water jacket according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Before the preferred embodiment of this invention is described and explained, the conventional mercury vapor lamp having water jacket means will first be described briefly.

Referring to FIG. 1, which illustrates the conventional structure of capillary type high-pressure mercury vapor lamp and the'mode of combination thereof with a water jacket, a support 14, to which an inner jacket tube 12 is attached, has a central opening in which a lamp supporting metal 16 is fixedly mounted through an electrical insulation 15 which may be made of rubber or plastic. The supporting metal 16 is formed, at the forward end, in the shape of a socket adapted to re ceive one 17 of the metallic base of a mercury vapor lamp 11. The electrical insulation 15 is wrapped around said forward end in fluid-tight fashion to form a Wilson seal, whereby the metallic base is electrically insulated from cooling water. The other metallic base 18 for the ground electrode of the lamp 11 engages in a socket 19, which is connected to the support 14 via a lead wire 20 extending through the cooling water.

To the support 14, on which the lamp 11 has been mounted in the above manner, is secured an outer jacket tube 13 through packings 21 and 22 and a mounting ring 23 in such a manner that the joint between the tube and support is water-tight.

In the above combination of lamp and jacket means, there is a possibility that the electrical insulation between the metallic base 17 and cooling water becomes insufficient and, moreover, the insulating 15 which is in direct contact with the metallic base is degraded as the base attains a high temperature, with the result that water leaks and a breakdown of the electrical insulation are encountered. In addition, replacement of the lamp involves an inconvenient procedure, i.e. holding the jacket assembly upright and detaching the outer jacket tube from the support.

Furthermore, the air bubbles which are formed when cooling water is admitted will not readily flow into the inner tube and thence to outside of the assembly.

Referring to FIG. 2 which illustrates this invention, an outer jacket tube 26 is made of a transparent material and an inner jacket tube 27, which is similarly made of a transparent material, is disposed within said outer tube 26.

Those jacket tubes are secured to a support 30, which is provided with a water inlet 28 and a water outlet 28a, by means of a mounting ring 25 through packings 31 and 32 and by a packing 33, respectively. The other end of the outer tube 26 has an opening 29, into which a lamp mounting metal support 32 is fitted and held by means of a locking nut 36 threaded on said support 32 and a holding 34 and a packing 35 tightly against the outer jacket tube 26 to provide a water-tight seal.

In addition, the lamp mounting support 32 is hollow and a lamp 40 is inserted through the opening in the support 32. The ground electrode 41 of the lamp 40 is secured, e.g. by soldering, to a metal base 42, which is fitted into, and supported by, a receptacle 43. The other base 47 is a hollow cylindrical ceramic base having a central collar 45, which is one of the salient features of this invention. This base is joined to the quartz lamp 40 by means of a heat-resilient cement, and an electrode 46 is secured, e.g. by soldering, to a metallic base 37, which is located at one end of the ceramic base 47. By means of a locking ring 39 adapted to be threaded into support 32 and compress a packing 38 between a central collar 45 of the above ceramic base 47 and the lamp mounting support 32, the lamp 40 is secured in position in water-tight, electrically insulated relation with respect to cooling water. In the above combination, replacement of the lamp can be easily carried out by suspending the inflow of cooling water and loosening the locking ring 39 to allow the water in the jacket to flow out through the water outlet 29. It is not necessary to detach the outer jacket tube 26.

The air bubbles which are formed in the outer tube 26 when cooling water is admitted readily finds its way into the inner tube 27, by virtue of the funnel-shaped flared opening of the tube 27 which is a feature of this invention, and ultimately flow out of tube 27. As explained before, the gap area defined between the outer tube and the flare accelerates the water flow and, thus, the air bubbles tending to dwell at such zone are effectively discharged through the flared opening out of the jacket.

In addition, by fabricating the inner tube 27 or outer tube 26, or both of them, from a material capable of absorbing thermal rays, instead of a mere transparent material, it is possible to obviate the deleterious effects of thermal radiation upon the surface to be illuminated.

Furthermore, because those tubes are cooled with water as described above, it is possible to prevent the overheating of the tubes themselves due to their absorption of thermal radiation. The following is an example of this invention.

For the outer tube, a clear glass is used and the inner tube is made of a filter glass which substantially restricts the transmittance of light having wavelengths of not more than 2800 angstrom units and not less than 5000 angstrom units and which has a maximum transmittance of 88 percent to light having a wavelength of 3650 angstrom units. Under saturated condition, the

temperature increase of the irradiated surface of the object is C. In a controlled experiment in which the same conditions as above are used except that both the inner and outer tubes are made of a clear glass the temperature increase is more than 30C.

The invention has been described in detail with particular reference to the preferred embodiment thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

I claim:

1. In a high pressure mercury vapor lamp having a mercury lamp element mounted between end supports and having a cooling water inlet means in one end support adjacent the outer periphery of the support and a cooling water outlet means adjacent the lamp element, that improvement comprising a double tube cooling jacket comprised of an outer transparent tube extending between the supports and mounted in water tight engagement with said supports, and an inner transparent tube within said outer tube and positioned around the lamp element and the water outlet means and having one end mounted on and extending from said one end support and having a free end adjacent and spaced from the other end support and having the free end flared outwardly with the outer end edgevof the flared portion defining a gap with the outer tube which is narrower than the space between the unflared portion of the inner tube and the outer tube, whereby any air bubbles trapped in the space between the outer tube and the inner tube and in the area at the end of the outer tube around the flared end of the inner tube are swept into the flared end of the inner tube and out of the outlet means during water flow through the space between the tubes and the space within the inner tube.

2. The improvement as claimed in claim 1 in which at least the inner tube is of a material which is capable of absorbing thermal radiation.

3. The improvement as claimed in claim 1 in which both the inner and outer tubes are of a material which is capable of absorbing thermal radiation. 

2. The improvement as claimed in claim 1 in which at least the inner tube is of a material which is capable of absorbing thermal radiation.
 3. The improvement as claimed in claim 1 in which both the inner and outer tubes are of a material which is capable of absorbing thermal radiation. 